Experimental study on the effects of farmed fish on the hydrodynamic characteristics of the net cage

The effects of farmed fish on both the drag force acting on and flow patterns inside and around the net cage are investigated experimentally. The laboratory experiments were conducted using a circular net-cage model with juvenile carp (Cyprinus carpio). The studied stocking density of the net cage ranges from 5.3 to 37.2 kg/m(3) depending on the number of fish. Four net-cage configurations are designed for the laboratory experiment. The drag force acting on the net cage and flow velocities as well as turbulence characteristics inside and downstream from the net cage are investigated. It is determined that biomass, flow speed, net-cage configuration, and net deformation have various effects on the drag force and fluid flow. The potential influence of fish size, swimming pattern of the fish school, and fish-net contact are also discussed. The motion of fish body and fins enhanced water mixing both inside and downstream from the net cage.